The State of the Circumstellar Medium Surrounding Gamma-Ray Burst Sources and its Effect on the Afterglow Appearance

We present a numerical investigation of the contribution of the presupernova ejecta of Wolf-Rayet stars to the environment surrounding gamma-ray bursts (GRBs), and describe how this external matter can affect the observable afterglow characteristics. An implicit hydrodynamic calculation for massive stellar evolution is used here to provide the inner boundary conditions for an explicit hydrodynamical code to model the circumstellar gas dynamics. The resulting properties of the circumstellar medium are then used to calculate the deceleration of a relativistic, gas-dynamic jet and the corresponding afterglow light curve produced as the shock wave propagates through the shocked-wind medium. We find that variations in the stellar wind drive instabilities that may produce radial filaments in the shocked-wind region. These comet-like tails of clumps could give rise to strong temporal variations in the early afterglow lightcurve. Afterglows may be expected to differ widely among themselves, depending on the angular anisotropy of the jet and the properties of the stellar progenitor; a wide diversity of behaviors may be the rule, rather than the exception.Comment: 17 pages, 7 figures, ApJ in pres

Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the Spitzer Space Telescope

We performed Spitzer Infrared Spectrograph mapping observations covering nearly the entire extent of the Cassiopeia A supernova remnant (SNR), producing mid-infrared (5.5-35 micron) spectra every 5-10". Gas lines of Ar, Ne, O, Si, S and Fe, and dust continua were strong for most positions. We identify three distinct ejecta dust populations based on their continuum shapes. The dominant dust continuum shape exhibits a strong peak at 21 micron. A line-free map of 21 micron-peak dust made from the 19-23 micron range closely resembles the [Ar II], [O IV], and [Ne II] ejecta-line maps implying that dust is freshly formed in the ejecta. Spectral fitting implies the presence of SiO2, Mg protosilicates, and FeO grains in these regions. The second dust type exhibits a rising continuum up to 21 micron and then flattens thereafter. This ``weak 21 micron'' dust is likely composed of Al2O3 and C grains. The third dust continuum shape is featureless with a gently rising spectrum and is likely composed of MgSiO3 and either Al2O3 or Fe grains. Using the least massive composition for each of the three dust classes yields a total mass of 0.02 Msun. Using the most-massive composition yields a total mass of 0.054 Msun. The primary uncertainty in the total dust mass stems from the selection of the dust composition necessary for fitting the featureless dust as well as 70 micron flux. The freshly formed dust mass derived from Cas A is sufficient from SNe to explain the lower limit on the dust masses in high redshift galaxies.Comment: 8 figures: Accepted for the publication in Ap

The cursed duet today: Tuberculosis and HIV-coinfection

The tuberculosis (TB) and HIV syndemic continues to rage and are a major public health concern worldwide. This deadly association raises complexity and represent a significant barrier towards TB elimination. TB continues to be the leading cause of death amongst HIV-infected people. This paper reports the challenges that lay ahead and outlines some of the current and future strategies that may be able to address this co-epidemic efficiently. Improved diagnostics, cheaper and more effective drugs, shorter treatment regimens for both drug-sensitive and drug-resistant TB are discussed. Also, special topics on drug interactions, TB-IRIS and TB relapse are also described. Notwithstanding the defeats and meagre investments, diagnosis and management of the two diseases have seen significant and unexpected improvements of late. On the HIV side, expansion of ART coverage, development of new updated guidelines aimed at the universal treatment of those infected, and the increasing availability of newer, more efficacious and less toxic drugs are an essential element to controlling the two epidemics. On the TB side, diagnosis of MDR-TB is becoming easier and faster thanks to the new PCR-based technologies, new anti-TB drugs active against both sensitive and resistant strains (i.e. bedaquiline and delamanid) have been developed and a few more are in the pipeline, new regimens (cheaper, shorter and/or more effective) have been introduced (such as the “Bangladesh regimen”) or are being tested for MDR-TB and drug-sensitive-TB. However, still more resources will be required to implement an integrated approach, install new diagnostic tests, and develop simpler and shorter treatment regimens

Wide-field global VLBI and MERLIN combined monitoring of supernova remnants in M82

From a combination of MERLIN (Multi-Element Radio-Linked Interferometer Network) and global VLBI (Very Long Baseline Interferometry) observations of the starburst galaxy M82, images of 36 discrete sources at resolutions ranging from ~3 to ~80 mas at 1.7 GHz are presented. Of these 36 sources, 32 are identified as supernova remnants, 2 are HII regions, and 3 remain unclassified. Sizes, flux densities and radio brightnesses are given for all of the detected sources. Additionally, global VLBI only data from this project are used to image four of the most compact radio sources. These data provide a fifth epoch of VLBI observations of these sources, covering a 19-yr time-line. In particular, the continued expansion of one of the youngest supernova remnants, 43.31+59.3 is discussed. The deceleration parameter is a power-law index used to represent the time evolution of the size of a supernova remnant. For the source 43.31+59.3, a lower limit to the deceleration parameter is calculated to be 0.53+/-0.06, based on a lower limit of the age of this source.Comment: 31 pages, 12 figures, 7 table

Assimilation in Multilingual Cities

We characterise how the assimilation patterns of minorities into the strong and the weak language differ in a situation of asymmetric bilingualism. Using large variations in language composition in Canadian cities from the 2001 and 2006 Censuses, we show that the differences in the knowledge of English by immigrant allophones (i.e. the immigrants with a mother tongue other than English and French) in English-majority cities are mainly due to sorting across cities. Instead, in French-majority cities, learning plays an important role in explaining differences in knowledge of French. In addition, the presence of large anglophone minorities deters much more the assimilation into French than the presence of francophone minorities deters the assimilation into English. Finally, we find that language distance plays a much more important role in explaining assimilation into French, and that assimilation into French is much more sensitive to individual characteristics than assimilation into English. Some of these asymmetric assimilation patterns extend to anglophone and francophone immigrants, but no evidence of learning is found in this case

Faster ground state energy estimation on early fault-tolerant quantum computers via rejection sampling

A major thrust in quantum algorithm development over the past decade has been the search for the quantum algorithms that will deliver practical quantum advantage first. Today's quantum computers and even early fault-tolerant quantum computers will be limited in the number of operations they can implement per circuit. We introduce quantum algorithms for ground state energy estimation (GSEE) that accommodate this design constraint. The first estimates ground state energies and has a quadratic improvement on the ground state overlap parameter compared to other methods in this regime. The second certifies that the estimated ground state energy is within a specified error tolerance of the true ground state energy, addressing the issue of gap estimation that beleaguers several ground state preparation and energy estimation algorithms. We note, however, that the scaling of this certification technique is, unfortunately, worse than that of the GSEE algorithm. These algorithms are based on a novel use of the quantum computer to facilitate rejection sampling. After a classical computer is used to draw samples, the quantum computer is used to accept or reject the samples. The set of accepted samples correspond to draws from a target distribution. While we use this technique for ground state energy estimation, it may find broader application. Our work pushes the boundaries of what operation-limited quantum computers are capable of and thus brings the target of quantum advantage closer to the present.Comment: 31 pages + appendix, 5 figure

A gain-of-function variant in <i>DIAPH1 </i>causes dominant macrothrombocytopenia and hearing loss

Macrothrombocytopenia (MTP) is a heterogeneous group of disorders characterized by enlarged and reduced numbers of circulating platelets, sometimes resulting in abnormal bleeding. In most MTP, this phenotype arises because of altered regulation of platelet formation from megakaryocytes (MK). We report the identification of DIAPH1, which encodes the Rho-effector diaphanous-related formin 1 (DIAPH1), as a candidate gene for MTP using exome sequencing, ontological phenotyping and similarity regression. We describe two unrelated pedigrees with MTP and sensorineural hearing loss that segregate with a DIAPH1 p.R1213* variant predicting partial truncation of the DIAPH1 diaphanous autoregulatory domain. The R1213* variant was associated with reduced proplatelet formation from cultured MKs, cell clustering and abnormal cortical filamentous actin. Similarly, in platelets there was increased filamentous actin and stable microtubules, indicating constitutive activation of DIAPH1. Over-expression of DIAPH1 R1213* in cells reproduced the cytoskeletal alterations found in platelets. Our description of a novel disorder of platelet formation and hearing loss extends the repertoire of DIAPH1-related disease and provides new insights into the autoregulation of DIAPH1 activity